Genetic Test Spares Many Breast Cancer Patients from Chemo

A landmark clinical trial has demonstrated that a genomic test called Prosigna can identify which breast cancer patients can safely skip chemotherapy without compromising their chances of survival. The findings, presented at the American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago, could reshape treatment decisions for hundreds of thousands of women worldwide.

The OPTIMA Trial

The international OPTIMA trial, led by University College London (UCL), enrolled 4,429 patients across six countries including the UK, Norway, Sweden, and Australia. Researchers compared standard chemotherapy followed by hormone therapy against a test-directed approach using the Prosigna genomic test, which analyzes the activity of 50 genes in tumor tissue to calculate a Risk of Recurrence (ROR) score.

According to The Guardian, patients with a low ROR score (≤60) received hormone therapy alone, while those with high scores received chemotherapy plus hormone therapy. The results were striking: five-year cancer-free survival rates were nearly identical — 94.8% for those who received chemotherapy and 93.6% for those who skipped it, demonstrating that the test-directed approach was non-inferior.

A Practice-Changing Result

Prof. Robert Stein, the trial’s lead investigator at UCL, described the findings as “practice-changing.” In a statement reported by BioSpace, he said: “Behind every breast cancer treatment decision is a patient asking, ‘Do I really need chemotherapy?’ OPTIMA answers this question with robust evidence.”

The study found that 68% of clinically high-risk patients could safely avoid chemotherapy entirely. This is particularly significant because chemotherapy carries severe side effects including hair loss, nausea, fatigue, cognitive impairment, nerve damage, and early menopause.

What Makes This Test Different

While similar genomic tests like MammaPrint and Oncotype DX already exist, the OPTIMA trial is groundbreaking because it validates the Prosigna test for broader patient populations — including premenopausal women aged 40-50 and patients with up to nine positive lymph nodes. Previous tests were primarily validated for postmenopausal women.

According to NOS, Dutch oncologist Gabe Sonke from the Antoni van Leeuwenhoek Hospital noted that the test’s effectiveness in younger women is particularly welcome news, as other genomic tests are only used for women over 50.

The Belgian Perspective

In Belgium, where 10,000 to 12,000 women are diagnosed with breast cancer annually, the news has been met with cautious optimism. Prof. Sevilay Altintas, an oncologist at University Hospital Antwerp (UZA), told Het Laatste Nieuws that the test represents “the next step toward personalized treatments.” However, she cautioned that the test is not yet available in Belgium and requires European regulatory approvals and reimbursement procedures, a process that could take several years.

Approximately 70-75% of breast cancer cases are hormone-sensitive (ER+/HER2-), making them potential candidates for this test. Currently, chemotherapy as an addition to surgery provides a cure for only 5-10% of breast cancer patients, yet many more receive it due to clinical uncertainty.

Implications for Patients

For patients, the implications are profound. The Guardian reported one trial participant described being able to skip chemotherapy as feeling “like Christmas.” Beyond the immediate relief from avoiding toxic side effects, the test enables more informed shared decision-making between patients and clinicians.

Prof. Iain MacPherson, co-chief investigator from the University of Glasgow, said: “Optima provides robust, practice-changing evidence that we can safely reduce the use of chemotherapy for many patients with hormone-sensitive breast cancer.”

What’s Next

While the results are promising, the Prosigna test is not yet available in Belgium or most European countries. Prof. Altintas expects urgency in the approval process, but regulatory and reimbursement hurdles remain. In the Netherlands, similar tests like MammaPrint and Oncotype DX have been reimbursed since 2023, setting a precedent that could accelerate adoption.

The OPTIMA trial’s findings are expected to influence clinical guidelines from organizations like ESMO and NICE, potentially paving the way for wider adoption of genomic testing in breast cancer care. For the thousands of women diagnosed each year, the era of personalized treatment decisions may be closer than ever.